Close-coupled towing linkage

ABSTRACT

A towing linkage is provided for connecting a first vessel to a second vessel and controlling the relative sway, surge, and yaw of the vessels to each other. The linkage comprises a first main resilient towing link for resiliently connecting the two vessels at their port sides, a second main resilient towing link for resiliently connecting the two vessels at their starboard sides, a first transverse resilient link for connecting the port side of the first vessel to the starboard side of the second vessel, and a second transverse resilient link for connecting the port side of the second vessel to the starboard side of the first vessel. The main resilient links provide surge control and the transverse links permit relative sway between the vessels while providing sway restraint. Pneumatic fenders can be placed between the two vessels to provide additional surge and yaw restraint.

United States Patent Roseman et al.

1 1 Mar. 18, 1975 CLOSE-COUPLED TOWING LINKAGE [75] Inventors: Donald P. Roseman, Rockville;

Milton Martin, Silver Spring; Eugene R. Miller, Annapolis, all of Md.

[73] Assignee: Hydronautics, Incorporated, Laurel,

[22] Filed: Aug. 31, 1973 [21] Appl. No.: 393,479

[52] US. Cl. 114/235 A, 114/77 R [51] Int. Cl B63b 21/00 [58] Field 01' Search 114/235 R, 235 A, 77 R, 114/213, 219; 280/408, 480; 294/74 R [56] References Cited UNITED STATES PATENTS 2,404,329 7/1946 Wallace 114/235 A 3,062,170 11/1962 Verneaux 114/235 R 3,079,192 2/1963 Otley 294/74 3,103,288 9/1963 Pruss 280/408 3,125,059 3/1964 Verneaux et 114/235 R 3,353,512 1l/1967 Mathews et a1 114/235 R 3,362,372 l/l968 Peterson 114/235 R 3,446,173 5/1969 Ohcho et a1. 114/235 R 3,645,225 2/1972 Lunde 114/235 R FOREIGN PATENTS OR APPLICATIONS 1,148,037 4/1969 United Kingdom 114/235 R Primary Examiner-Trygve M. Blix Assistant ExaminerGalen L. Barefoot Attorney, Agent, or FirmFinnegan, Henderson, Farabow and Garrett [57] ABSTRACT A towing linkage is provided for connecting a first vessel to a second vessel and controlling the relative sway, surge, and yaw of the vessels to each other. The linkage comprises a first main resilient towing link for resiliently connecting the two vessels at their port sides, a second main resilient towing link for resiliently connecting the two vessels at their starboard sides, a first transverse resilient link for connecting the port side of the first vessel to the starboard side of the second vessel, and a second transverse resilient link for connecting the port side of the second vessel to the starboard side of the first vessel. The main resilient links provide surge control and the transverse links permit relative sway between the vessels while providing sway restraint. Pneumatic fenders can be placed between the two vessels to provide additional surge and yaw restraint.

8 Claims, 6 Drawing Figures CLOSE-COUPLED TOWING LINKAGE BACKGROUND OF THE INVENTION This invention relates to a towing linkage and more particularly to close-coupled towing linkages.

In the past it has been a common practice, when one vessel, such as a tug, towed a train of barges, to provide a relatively long towline to connect the tug to the first barge in the train and provide additional towlines to connect the remaining barges in the train to the tug or to other barges. Long towlines are required to provide shock absorbtion between the tug and first barge and between successive barges. The use of multiple towlines presented many disadvantages because the towlines tended to become fouled and a considerable amount of effort was needed to link each towline to the tug and barges. Also, the towlines create a drag and provide a limited capacity for controlling and maneuvering one or more barges in a seaway.

In the past, when one vessel pushed another, for example, when a tug pushed one or more barges, it has been a common practice to interconnect the vessels by rigid structural members in a close-coupled linkage. These prior art systems have been subject to structural failure because of the stresses created during towing. Further, the prior art systems for pull towing and push towing generally have not been able to provide as much control over the vessels as would be desirable and have had deficiencies in their ability to restore the vessels to an equilibrium position.

Accordingly a continuing search has been going on for improved coupling arrangements for close-coupled ocean towing which would provide improved control of the towing and towed vessels. Such a coupling arrangement should be able to provide control in either a pushtow or pull-tow situation and be adaptable to tow multiple barges in linear flotilla without intermediate towlines. The coupling should permit relative motions between the vessels, including pitch, roll, yaw, sway, surge and heave while providing yaw, surge, and sway restraining and restoring forces without causing excessive lateral forces.

SUMMARY OF THE INVENTION In accordance with its purpose, as embodied and broadly described, the present invention comprises a towing linkage for connecting a first vessel to a second vessel and includes a first main resilient towing link for resiliently connecting the two vessels at their port sides; a second main resilient towing link for resiliently connecting the two vessels at their starboard sides; a first transverse resilient link for connecting the port side of the first vessel to the starboard side of the second vessel; and a second transverse resilient link for connecting the port side of the second vessel to the starboard side of the first vessel.

The towing linkage of the present invention permits relative yaw, surge, sway, roll, pitch and heave between the vessels, but limits the amount of relative yaw, surge, and sway by providing yaw, surge, and sway restoring forces.

The transverse links permit relative sway while providing sway restraint. Preferably, the transverse links each comprise a wire cable connected at one end to one of the vessels and at its other end to a spring mounted on the other of the vessels. It is also preferred that each wire cable have a fitting at its center to prevent chafing of the wire cables at their crossing point.

In one embodiment of the invention, the first and second main links each include a single acting spring and a pneumatic fender means is positioned between the first and second vessels to control relative surge of the first and second vessels. The combination of spring and fender means also serves to provide yaw restraint while permitting a limited amount of yaw. In an alternate embodiment of the invention, the first and second main links each include double acting springs which provide relative surge and yaw restraint while permitting limited amount of these motions.

It is to be understood that both the foregoing and general description and the following detailed description are exemplary and explanatory and are not restric tive of the invention.

DETAILED DESCRIPTION OF THE INVENTION The accompanying drawings illustrate an example of a preferred embodiment of the invention and together with the description serve to explain the principles of the invention.

FIG. I is a perspective view of a towing linkage constructed in accordance with the teachings of the present invention and showing two pneumatic fenders.

FIG. 2 is a side elevational view ofthe towing linkage shown in FIG. I showing a pneumatic fender in an uncompressed state;

FIG. 3 is a side elevational view of the towing linkage of FIG. I and showing the pneumatic fender in a com pressed state;

FIG. 4 is a top view of the towing linkage of FIG. I;

FIG. 5 is a top view of an alternate embodiment of the present invention;

FIG. 6 is a side elevational view of the towing linkage shown in FIG. 5.

Referring to the drawings, there is shown in FIGS. 1 to 4 a towing linkage, generally I0, connecting a first vessel generally I2 to a second vessel, generally [4.

Vessel 12 is a lead vessel and includes a port side 16, a starboard side 18, a stern 20, and a bow 22. Similarly, vessel 14 is a following vessel and includes a port side 24, a starboard side 26, a stem 28 and a bow 30. Stem 20 of lead vessel I2 includes a pushing knee 32 and how 30 of following vessel 14 includes a pushing knee 34.

Both the lead vessel 12 and following vessel 14 are subjected independently to the force of the wind, the waves, and perhaps currents tending to make them more linearly or rotationally about their longitudinal, lateral or vertical axes and thus pitch, heave, roll, yaw, sway, and/or surge. In pitching, the vessel rotates, that is, alternately plunges and rises about its lateral axis shown as axis X in FIG. 1. In rolling, the vessel rotates about its longitudinal axis, which is shown as Y in FIG. I. In yawing, the vessel will swing to one side or the other from its course, that is, it will rotate about its vertical axis Z. In heaving, the vessel alternately rises and falls more or less without pitching and rolling, that is, it moves linearly along its vertical axis shown as axis 2 in FIG. 1. In swaying the vessel is displaced sidewise back and forth, that is, it moves linearly along its lateral X axis. In surge, the vessel moves linearly along its longitudinal axis Y. These three linear motions and three rotational motions completely define any movement of the vessel from an analytical standpoint.

In accordance with the invention, a first main resilient towing link is provided for resiliently connecting the two vessels at their port sides. As here embodied, and as shown in FlGS. l to 4, a first towing link. generally 36, connects port side 16 of the stem 20 of lead vessel 12 with port side 24 of the bow 30 of following vessel 14. Towing link 36 includes a wire cable 38 and a spring 40. Cable 38 is connected at one end to a deck pad 42 mounted on the port side 24 of the deck of pushing knee 34 of following vessel 14 and at its other end of spring 40 which is mounted on the port side 16 of the deck of pushing knee 32 of lead vessel 12. Cable 38 passes through a self-aligning fairlead 44 mounted on the port side aft of the deck of pushing knee 32. A suitable fairlead for use in the present invention can be obtained commerically from Smith-Berger of Seattle, Washington.

The longitudinal axis of spring 40 is parallel to the longitudinal axis of vessels l2 and 14. Spring 40 preferably is a single acting spring. The exact specifications of spring 40, of course, as will be understood by those skilled in the art, can be varied to meet the requirements of each towing and towed vessel system and sea conditions that are to be encountered. Spring 40 can be of linear or non-linear character and can be either pneumatic, hydraulic, mechanical or elastomeric. First main link 36, as described in greater detail hereafter, acts to restrain surge of vessels 12 and 14, while permitting a limited amount of surge.

In accordance with the invention, a second main resilient towing link is provided for resiliently connecting the two vessels at their starboard sides. As here embodied. and as best seen in FIG. 4, a second towing link. generally 46, connects the starboard side 18 of the stern 20 of lead vessel 12 with the starboard side 26 of the bow 30 of the following vessel 14. Towing link 46 includes a wire cable 48 and a spring 50. Cable 48 is connected at one end to a deck pad 52 mounted on the starboard side 26 of the deck of pushing knee 34 of following vessel l4 and at its other end to spring 50 which is mounted on the starboard side 18 of the deck of pushing knee 32 of lead vessel 12. Cable 48 passes through a self-aligning fairlead 54 mounted on the starboard side l8 of the rear of the deck of pushing knee 32. Fairlead 52 is similar to and preferably is identical to fairlead 44 of first towing link 36.

The longitudinal axis of spring 50 is parallel to the longitudinal axes of vessels l2 and 14. Spring 50 preferably is identical to spring 40 of the first towing link 36. Spring 50 thus can be of linear or non-linear character and can be either pneumatic. hydraulic, mechanical or elastomeric. The spring characteristics of spring 50 preferably are identical to those of spring 40 to provide a symmetrical arrangement and equal capacity for surge control on both sides of the lead and following vessels so that an even control of surge can be main tained. The exact specifications of spring 50, of course. can be varied to meet specific towing requirements and conditions.

In accordance with the invention, a first transverse resilient link is provided for resiliently connecting the port side of the first vessel to the starboard side of the second vessel. As here embodied, a first resilient diagonal link. generally 56, connects the starboard side 18 of the stern 30 of lead vessel l2 with the port side 24 of the bow 30 of following vessel l4. Diagonal link 56 comprises a steel wire cable 58 and a spring 60. Cable 58 is connected at one end to a deck pad 62 mounted inboard and adjacent to deck pad 42 on the port side 24 of the deck of pushing knee 34 of following vessel 14 and at its other end to spring 60 which is mounted on the starboard side 18 of the deck of pushing knee 32 of lead vessel 12. Deck pad 62 is positioned between deck pad 42 and the longitudinal center axis of following vessel 14. Cable 58 preferably is zinc coated to provide protection against the elements. Cable 58 passes through a self-aligning fairlead 64 mounted on the starboard side of the rear of the deck of pushing knee 32 of lead vessel 12.

The longitudinal axis of spring 60 is parallel to the longitudinal axes of vessels l2 and 14. Spring 60 is a single acting spring. The exact specifications of spring 60, of course, as will be understood by those skilled in the art, can be varied to meet specific towing requirements and conditions. Spring 60 can be of linear or non-linear character and can be either pneumatic. hydraulic, mechanical or elastomeric.

In accordance with the invention. a second transverse resilient link is provided for resiliently connecting the starboard side of the following vessel to the port side of lead vessel. As here embodied, a second diagonal link, generally 66, connects the port side 16 of the stem 20 of lead vessel 12 with the starboard side 26 of the bow 30 of following vessel 14.

Diagonal link 66 comprises a wire cable 68 and a spring 70. Cable 68 is connected at one end to a deck pad 72 mounted inboard and adjacent to deck pad 52 on the starboard side 26 of the deck of pushing knee 34 of following vessel 14 and at its other end to spring 70 which is mounted on the port side 16 of the deck of pushing knee 32 of lead vessel 12. Deck pad 72 is positioned between deck pad 52 and the longitudinal center axis of following vessel 14. Cable 68 preferably is zinc coated to provide protection against the elementsv Cable 68 passes through a self-aligning fairlead 74 mounted on the port side of the rear of the deck of pushing knee 32 of lead vessel 12. Fairlead 74 prefera bly is identical to fairlead 64 of first diagonal towing link 56.

The longitudinal axis of spring 70 is parallel to the longitudinal axis of vessels l2 and 14. Spring 70 is identical to spring 60 of first diagonal towing link 56 and thus is a single acting spring and can be of linear or non-linear character and can be either pneumatic, hydraulic, mechanical or elastomeric. Diagonal links 56 and 66, as described in greater detail hereafter, primarily act to restrain sway while permitting a limited amount of relative sway between vessels l2 and 14. Diagonal links 56 and 66 also act to provide yaw and surge restraint while permitting limited amounts of these motions. The spring characteristics of spring 70 preferably are identical of those of spring 50 to provide equal capacity for sway restraint on both sides of the towing and towed vessels so that an even control of sway can be maintained. The exact specifications of spring 70, of course, can be varied to meet specific towing requirements and conditions.

First diagonal link 56 and second diagonal link 66 are symmetrically arranged with respect to each other about the longitudinal center axis of vessels l2 and l4. and their wire cables 58 and 68 diagonally pass over or under each other in the space between stern 20 of lead vessel 12 and how 30 of followed vessel 14. Each cable 58 and 68 as seen in FIG. 4, is provided with a protecting means such as a fiber reinforced elastomeric sleeve 76 at the point where the two cables cross each other to prevent the cables from chaffing each other at this crossing point.

In a preferred embodiment of the invention, a pneumatic fender means is provided between the first and second vessels to provide surge and yaw restraint. As here embodied, one or more pneumatic fenders, and as shown in FIGS. 1 to 4, two pneumatic fenders 78 and 80, are provided between the stem of lead vessel 12 and bow of following vessel 14. Each pneumatic fender 78 and 80 is of essentially cylindrical geometry and has spherical or eliptical ends. Pneumatic fender 78 has opposing ends 82 and 84, and similarly pneumatic fender 80 has opposing ends 86 and 88. Preferably, pneumatic fender 78 is provided with a wire net, generally 90, knit from a wire cable, and pneumatic fender 80 is provided with a similar wire net 92, to facilitate handling and securing in place of the pneumatic fenders.

Protecting means preferably are provided for the wire cable of wire nets 90 and 92 to prevent the wire cable from chafing and damaging the pneumatic fenders and vessels. As here embodied and as shown in FIGS. 2 to 4, the protecting means is in the form of automobile tires 94 that are secured to the pneumatic fenders and the wire cable is passed through these tires. As will be apparent to those of ordinary skill in the art, other well-known protecting means can be used.

Pneumatic fenders 78 and 80 are arranged in a row so that their longitudinal axes are aligned with each other and are perpendicular to the longitudinal axes of vessels l2 and 14 to enable the cylindrical side walls of each of the fenders to contact stem 20 of lead vessel 12 and pushing knee 34 of following vessel 14.

Pneumatic fenders 78 and 80 are secured to each other in a row by tying one end of pneumatic fender 78 to one end of pneumatic fender 80. As best seen in FIG. 4, this can be accomplished by securing the ends of wire net 90 adjacent end 84 of pneumatic fender 78 to a shackle 96, and by securing the ends of wire net 92 adjacent end 86 of pneumatic fender 80 to the same shackle 96. The row of pneumatic fenders 78 and 80 is secured to lead vessel 12 by tying the outer ends of the row to lead vessel 12. To accomplish this the ends of wire net 90 adjacent outer end 82 of pneumatic fender 78 are secured to a shackle 98. Two vertically spaced pads 102 and 104 (FIG. 2) are recessed into the starboard sidewall of lead vessel 12. Guy rope 106 connects pad 102 to shackle 98 and a second guy rope 108 connects pad 104 to shackle 98. Similarly, the outer end 88 of pneumatic fender 80 is connected to port sidewall of lead vessel 12 by two guy ropes which connect two vertically spaced recessed pads on the port sidewall of lead vessel 12 to a shackle 100 (FIG. 4) which receives the outer ends of wire net 92. The guy ropes preferably are zinc coated marine mooring cable.

Pneumatic fenders 78 and 80 are air filled, are constructed of reinforced rubber or similar material and have safety valves to permit pressure relief before a bursting pressure is reached. Suitable pneumatic fenders for use in the present invention are commerically obtainable from The Yokohama Rubber Co., Ltd., Tokyo. Japan. As will be understood by those skilled in the art, the exact size and number of pneumatic fenders in the row between lead vessel 12 and following vessel 14 is dependent on such factors as the width and weight of the lead and following vessels.

In operation. and prior to the beginning of a voyage, springs 40, 50, 60 and and their corresponding wire cables 38, 48, 58, and 68 are prestressed to a predetermined loading, thereby resulting in a preloading and compressing of pneumatic fenders 78 and as shown in FIG. 3.

In the preloaded condition, the linkage system permits six degrees of motion of lead vessel 12 with respect to following vessel 14, but provides motion restraining and restoring forces in three of these degrees of motion. Thus, no external motion restraining or restoring forces are provided for pitch, roll, and heave except for existing or inherently occurring hydrodynamic and hydrostatic forces, while surge, sway and yaw restraint are provided by the linkage system.

Surge restraint is provided by first linkage 36, second linkage 46 and pneumatic fenders 78 and 80. For example, when lead vessel 12 is given a surging force which tends to force it ahead of its normal relative position with respect to following vessel 14, springs 50 and 60 of first linkage 36 and second linkage 46 will first compress to permit surge to occur, but because of their resilient properties, they will absorb energy and reduce the amount of surge force that is transmitted to lead vessel 12. As soon as the surging force acting on lead vessel 12 disappears or is reduced, springs 40 and 50 will begin returning to their preloaded condition and bring lead vessel 12 back towards it normal relative position with respect to following vessel 14.

When following vessel 14 is given a surging force which tends to force it ahead of its normal relative position with respect to lead vessel 12, pneumatic fenders 78 and 80 will compress and absorb energy to limit the amount of relative surge that will occur. As soon as the surging force acting on following vessel 14 is absorbed, pneumatic fenders 78 and 80 will begin expanding to their preloaded condition and bring following vessel 14 back toward the equilibrium position with respect to lead vessel 12.

Sway restraint is provided by first diagonal link 56 and second diagonal link 66. For example, when a force is applied to lead vessel 12 which tends to linearly move the longitudinal axis of vessel 12 toward the port side 24 of following vessel 14, spring 70 ofdiagonal link 66 is compressed. Wire cable 68 because of its diagonal positioning on vessels l2 and 14, acts both in the lateral direction and in the longitudinal direction. The lateral component of wire cable 68 will cause spring 70 to absorb energy and limit the amount of sway oflead vessel 12 toward the port side 24 of following vessel 14. As soon as the sway force is absorbed, spring 70 will begin returning to its normal preloaded position and bring lead vessel 12 back to its equilibrium position relative to following vessel 14.

Similarly, if a swaying force is appled to lead vessel 12 which tends to move its longitudinal axis linearly toward the starboard side 26 of following vessel 14, spring 60 of diagonal link 56 is compressed. Diagonal link 66 operates in a similar manner to, but in an opposite direction from diagonal link 56 so that diagonal link 66 will first restrain and then restore lead vessel l2 to its equilibrium position when it is swayed toward the starboard side of following vessel l4.

As will be apparent to those skilled in the art, diagonal link 66 provides sway control for following vessel 14 when its longitudinal axis is forced toward the port of lead vessel 12, and diagonal link 56 provides sway control for following vessel when its longitudinal axis is forced toward the starboard oflead vessel 12. Also, because diagonal links 56 and 66 have longitudinal acting components, they act in a similar manner to links 36 and 46 and contribute to surge control.

Yaw restraint is provided primarily by pneumatic fenders 78 and 80 and secondarily by diagonal links 56 and 66. Pneumatic fenders 78 and 80 can be obliquely compressed to absorb energy when either vessel 12 or 14 is rotated about its vertical axis. For example, if lead vessel 12 is rotated clockwise as viewed in FIG. 1, the outer end 82 of pneumatic fender 78 will be compressed and absorb energy to reduce the amount of yaw acting on vessel 12. When the yaw producing forces disappear or are reduced, pneumatic fender 78 will begin returning lead vessel 12 to its equilibrium position with respect to following vessel 14. Link 36 and diagonal link 66 also produce yaw restraining forces and aid pneumatic fender 78 in controlling yaw.

Simiarly, if lead vessel 12 is rotated counterclockwise as viewed in FIG. 1, the outer end 88 of pneumatic fender 80 will be compressed and absorb energy to first reduce the amount of yaw acting on vessel 12 and then return the vessel towards its normal relative position with respect to following vessel 14 when the yaw producing forces disappear or are reduced. Link 46 and diagonal link 56 also create yaw restraining forces and aid pneumatic fender 80 in controlling yaw.

As will be apparent to those skilled in the art, when following vessel 14 is subjected to yaw producing forces. pneumatic fenders 78 and 80 act in a similar but opposite manner to that just described to restrain and restore following vessel 14 to its normal position relative to lead vessel 12.

The towing linkage of the present invention thus permits relative surge, yaw and sway motions between the vessels while limiting the amount of these motions. The vessels are free to roll, heave and pitch with respect to each other.

Lead vessel 12, as will be understood by those skilled in the art, can be the first barge in a train of barges that is being pulled by a tub, and following vessel 14 can be the second barge in the train. In this arrangement, the bow of lead vessel 12 would be connected to the tug by a towline in a conventional manner. Additional barges can be added to the train by using the towing linkage of the present invention to connect each succeeding barge to the immediately preceeding barge. The towing linkage of the present invention can also be used to connect a tug to a barge in a push tow arrangement where the tug pushes the barge or a train of barges. The barges in the train, of course, would be connected to each other by using the towing linkage of the present invention between each two adjacent barges.

In an alternate embodiment of the invention, and as seen in FIGS. and 6, pneumatic fenders 78 and 80 are removed. In this embodiment of the invention, a first main resilient towing link generally 120, connects a lead vessel 122 with a following vessel 124 at their ports. Towing link 120 comprises a double acting spring 126 positioned between the stern of lead vessel 122 and the bow of following vessel 124, an axially aligned strut 130 which connects spring 126 to lead vessel 122 and an axially aligned strut 130 which connects spring 126 to following vessel 124. A pedestal bearing 129 connects strut 128 to the port side of lead vessel 122 and a pedestal bearing 131 connects strut 130 to the port side of following vessel 124. Spring 126 permits struts 128 and 130 to rotate with respect to each other about their axes. Pedestal bearings 129 and 133 permit first link to freely rotate in a horizontal plane and rotate in a vertical plane.

A second main resilient towing link, generally 132 connects lead vessel 122 with following vessel 124 at their starboard sides. Towing link 132 comprises a double acting spring 134 positioned between the stern of lead vessel 122 and the bow of following vessel 124, an axially aligned strut 136 which connects spring 134 to lead vessel 122, and an axially aligned strut 138 which connects spring 134 to following vessel 124. A pedestal bearing 140 connects strut 136 to lead vessel 122 and a pedastal bearing 142 connects strut 138 to following vessel 124. Spring 134 permits struts 136 and 138 to rotate with respect to each other about their axes. The ability of struts 128 and to rotate relative to each other and of struts 136 and 138 to rotate relative to each other permits relative roll between the vessels to occur. Pedestal bearings and 142 permit second link 132 to freely rotate in a horizontal plane and rotate in a vertical plane.

Springs 126 and 134 are identical double acting springs and can be of linear or non-linear character, and of pneumatic, hydraulic, mechanical or elastomeric type.

A first diagonal link, generally, 144, connects the starboard side of lead vessel 122 with the port side of following vessel 124. Diagonal link 144 comprises a wire cable 146 and a single acting spring 148. Cable 146 is connected at one end to a deck pad 150 mounted inboard and adjacent to pedestal bearings 131 on the port side of the deck of following vessel 124, and after passing through a fairlead 152 mounted on the starboard side of the deck of lead vessel 122 is connected at its other end to spring 148 which is mounted on the starboard side of the deck oflead vessel 122. Diagonal link 144 is substantially identical in design and function to diagonal link 56 of FIGS. 1 to 4.

Similarly, a second diagonal link, generally 154, connects the port side of lead vessel 122 with the starboard side of following vessel 124. Diagonal link 154 comprises a wire cable 156 and a single acting spring 158. Cable 156 connected at one end to a deck pad 160 mounted inboard and adjacent to pedestal bearing 142 on the starboard side of the deck of the following vessel 124, and after passing through a fairlead 162 mounted on the port side of the deck of lead vessel 122 is connected at its other end to spring 158 which is mounted on the port side of the deck of lead vessel 122. Diagonal link 154 is substantially identical in design and function to diagonal link 66 of FIGS. 1 to 4.

In operation, diagonal links 144 and 154 permit relative sway but provide sway restraint in a manner similar to diagonal links 56 and 66 of FIGS. 1 to 4. In this embodiment of the invention, however, first and second resilient links 120 and 132 provide the surge and yaw control ofthe sytem. Thus, when either lead vessel 122 or following vessel 124 is subjected to surge forces, double acting springs 126 and 134 act in a corresponding axial direction to limit the amount of relative longitudinal movement of the vessels and restore the relative positions of the vessels when the surge forces disappear or are reduced. Springs 126 and 134 act in the same direction when providing surge restraint. When either lead vessel 122 or following vessel 124 is subjected to yaw producing forces, double acting springs 126 and 134 act in opposing directions to limit the amount of relative yaw of the vessels and restore the relative positions of the vessels when the yaw producing forces disappear or are reduced.

The present invention thus permits free motion in pitch, roll and heave, but restrains motion in surge, sway and yaw while permitting these motions to occur to a limited extent. This arrangement serves to relieve lateral bending forces and limit yaw motion which has been a problem with prior art linkages. The present invention can be used to tow or push multiple barges in linear flotilla, without intermediate tow lines, for ocean going service. Thus, the bow of one vessel can be connected to the stern of another vessel with the linkage of the present invention and this linkage can be repeated many times over in a series of vessels. The linkage of the present invention can be used either as a pull-tow system or a push-tow system and provides similar controls of sway, yaw and surge in each type of system.

The invention in its broader aspects is not limited to the specific details shown and described and departures may be made from such details without departing from the principles of the invention and without sacrificing its chief advantages.

What is claimed is:

l. A towing linkage of connecting a first vessel to a second vessel and permitting relative yaw. surge and sway while limiting the amount of these motions comprising in combination:

a. a first main resilient towing link for resiliently connecting the two vessels at their port sides;

b. a second main resilient towing link for resiliently connecting the two vessels at their starboard sides, said main resilient towing links permitting surge between the vessels while providing surge restraint;

c. a first transverse resilient link for connecting the port side of the first vessel of the starboard side of the second vessel;

d. a second transverse resilient link for connecting the port side of the second vessel to the starboard side of the first vessel, said transverse links permitting relative sway between the vessels while providing sway restraint; and

e. pneumatic fender means between the first and second vessels to provide surge and yaw restraints.

2. The linkage of claim I wherein said transverse links each comprise a wire cable connected at one end to one of the vessels and at its other end to a spring mounted on the other of said vessels.

3. The linkage of claim 2 including a fitting for preventing chafing of the wire cables of the transverse links at their crossing point.

4. The linkage of claim 1 wherein said first and second main resilient towing links each include a single acting spring mounted on one of said vessels.

5. The linkage of claim 4 wherein said transverse links each comprise a wire cable connected at one end to one of the vessels and at its other end to a spring mounted on the other of said vessels.

6. The linkage of claim 1, wherein the pneumatic fender means comprises at least one inflatable resilient fender of generally cylindrical geometry, said fender being secured between the two vessels with its cylindrical side walls in contact with the stern of the leading vessel and the bow of the following vessel.

7. The linkage of claim 6, wherein the fender is a cy lindrical rubber fender of relatively large diameter and has spherical ends.

8. The linkage of claim 7, including a plurality of dis crete pneumatic fenders interconnected and extending in a row between the two vessels with their axes longi tudinally aligned and perpendicular to the axes of the vessels. 

1. A towing linkage of connecting a first vessel to a second vessel and permitting relative yaw, surge and sway while limiting the amount of these motions comprising in combination: a. a first main resilient towing link for resiliently connecting the two vessels at their port sides; b. a second main resilient towing link for resiliently connecting the two vessels at their starboard sides, said main resilient towing links permitting surge between the vessels while providing surge restraint; c. a first transverse resilient link for connecting the port side of the first vessel of the starboard side of the second vessel; d. a second transverse resilient link for connecting the port side of the second vessel to the starboard side of the first vessel, said transverse links permitting relative sway between the vessels while providing sway restraint; and e. pneumatic fender means between the first and second vessels to provide surge and yaw restraints.
 2. The linkage of claIm 1 wherein said transverse links each comprise a wire cable connected at one end to one of the vessels and at its other end to a spring mounted on the other of said vessels.
 3. The linkage of claim 2 including a fitting for preventing chafing of the wire cables of the transverse links at their crossing point.
 4. The linkage of claim 1 wherein said first and second main resilient towing links each include a single acting spring mounted on one of said vessels.
 5. The linkage of claim 4 wherein said transverse links each comprise a wire cable connected at one end to one of the vessels and at its other end to a spring mounted on the other of said vessels.
 6. The linkage of claim 1, wherein the pneumatic fender means comprises at least one inflatable resilient fender of generally cylindrical geometry, said fender being secured between the two vessels with its cylindrical side walls in contact with the stern of the leading vessel and the bow of the following vessel.
 7. The linkage of claim 6, wherein the fender is a cylindrical rubber fender of relatively large diameter and has spherical ends.
 8. The linkage of claim 7, including a plurality of discrete pneumatic fenders interconnected and extending in a row between the two vessels with their axes longitudinally aligned and perpendicular to the axes of the vessels. 